The present invention relates to an aircraft having an illumination device, and in particular to an aircraft having an illumination device which by a corresponding selection of the wavelength and of the irradiation angle prevents a person situated in the aircraft from becoming tired or sleepy.
There exists a biological light effect on humans that acts as a result of the action of light of a particular wavelength on certain regions in the eye. These regions are outside the eye's region that is responsible for visual perception. It has been recognised that the action of light falling onto the retinohypothalamic tract affects, for example, control of the hormone melatonin, which hormone is responsible for controlling tiredness and wake states, and further affects regulation of the circadian rhythm, which reflects the change between the wake state and the state of tiredness or sleepiness. The retinohypothalamic tract is an arrangement of photosensitive cells on the retina, which cells occur in an aggregated manner on the lower part of the retina. These cells comprise the light-sensitive pigment melanopsin that converts light to electrical signals. The so-called suprachiasmatic nucleus (SCN) is driven by these signals and influences the pineal gland, which in turn regulates hormone release. This hormone control then provides the corresponding predetermined values for setting the inner biological clock of humans. For this reason an increase in the melatonin level, for example at night, results in considerable tiredness or sleepiness, while a reduction in the level of sleep hormone sets the organism to “waking up”. This non-optical system reacts best to essentially monochromatic light with a wavelength of 464 nanometres, which essentially corresponds to the blue colour of the sky. If a special non-optical receptor in the eye, which receptor is preferably found in the lower half of the retina, is irradiated with short-wave light of approximately 464 nanometres, then melatonin production stops so that melatonin suppression occurs. In this process, even small quantities of light of a wavelength of 464 nanometres are sufficient to influence melatonin production.